Vascular filter convertible to a stent and method

ABSTRACT

A vascular filter for temporary or permanent implantation within a body vessel to filter particulates or thrombus in the blood stream, is capable of being converted some time after initial implantation into a tubular stent. In this configuration, the stent tends to hold the vessel open without any significant filtering effect. The convertible filter/stent may have a tubular metal mesh structure. Also, the device may form one or more filter lattices when in the filter configuration.

This application is divisional of U.S. patent application Ser. No. 09/342,876, which filed Jun. 29, 1999 claims the benefit of U.S. Provisional Application No. 60/090,968 filed Jun. 29, 1998.

BACKGROUND AND SUMMARY OF THE INVENTION

1. Technical Background

The present invention relates generally to medical devices, and more particularly to a vascular medical device.

2. Discussion

Vascular filters may be used for a variety of therapeutic applications, including implantable vena cava filters for capturing thrombus, or for distal protection during a vascular procedure.

Numerous different vascular filters are known of various types and designs. Prior filters are generally designed for either temporary use, such as may be provided on a catheter or provided with a mechanism for retrieving, the filter, or for permanent implantation. Either a permanent or a temporary filter maybe preferred for a specific situation, given the specific therapeutic conditions and the properties of the filter.

The present invention relates to a filter system including a vascular filter that can be placed inside a body passage or cavity, such as a blood vessel, through a catheter consisting of a tubular basic body with a distal end, a proximal end and a catheter lumen extending in between the ends. The vascular filter can be received in a compressed state inside the catheter lumen, and the catheter is provided with an ejection device which can be used to eject the vascular filter from the distal end of the catheter.

Vascular filters of the type that are implanted in a patient's body vessel are often made of an elastic or so-called “memory” material. The vascular filter is positioned by using an ejection member to push the filter from the open distal tip of the catheter into the blood vessel.

Many prior vascular filters expand resiliently from the compressed state inside the catheter lumen to an enlarged or deployed state, when released or deployed at the desired site for treatment.

However, it is desirable to provide a filter capable of being implanted for a selectively variable duration. For example, a vascular filter according to the present invention might have a design such that the filter is deployed through a catheter, and then the filter may be transformed at a selected time later to provide an open “through lumen”.

The present invention provides a novel vascular filter having a hybrid configuration, which is capable of being transformed to provide a through lumen at a time selected later.

Accordingly, it is desirable to provide a vascular filter capable of being implanted in an initial “filtering” configuration. The device may be monitored periodically for a time, until the physician decides to convert the implanted filter into a stent, for example. The filter is thus designed to selectively metamorphose into a second stent or graft configuration, providing a resilient tubular scaffold having and tending to maintain an open lumen through the body passageway.

Of course, the present invention relates broadly to vascular filters that are convertible into an open lumen device. The present invention may therefore be practiced in a multitude of different designs and variations which will occur to an average practitioner in the art.

These and various other objects, advantages and features of the invention will become apparent from the following description and claims, when considered in conjunction with the appended drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagrammatic side elevational view of a convertible vascular filter, arranged according to one embodiment of the principles of the present invention;

FIGS. 2 and 3 are diagrammatic side elevational views of the convertible vascular filter, showing operation of the device during transformation;

FIG. 4 is a diagrammatic side elevational view of the vascular filter of FIG. 1, after transformation into a stent;

FIG. 4A is an axial longitudinal view of the stent of FIG. 4;

FIG. 5 shows a convertible vascular filter arranged according to the principles of the present invention in an initial filter configuration before being trasformed into a stent configuration;

FIG. 6 shows the vascular filter of FIG. 5, after a catheter has snared a proximal end hook of the filter; and

FIG. 7 shows the vascular filter of FIG. 6, after the proximal end of the filter has been opened, and illustrating the distal end hook being snared;

FIG. 8 shows the vascular filter of FIG. 7, after a catheter has snared a distal end hook of the filter;

FIG. 9 shows the convertible vascular filter of FIGS. 5-8, after being transformed into a tubular stent;

FIG. 10 is a partial view of the catheter and snare system of FIGS. 5-8 in greater detail;

FIG. 11 is a side elevational view of yet another embodiment of a convertible vascular filter, arranged according to the present invention; and

FIG. 12 is a side elevational view of the vascular filter of FIG. 11, showing the filter being converted into a stent by inflating the end portions with a balloon catheter.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The following description of the preferred embodiments of the present invention is merely illustrative in nature, and as such it does not limit in any way the present invention, its application, or uses. Numerous modifications may be made by those skilled in the art without departing from the true spirit and scope of the invention.

Referring to the drawings, in FIG. 1 a vascular fiter 10 according to the present invention has been illustrated. According to the specific embodiment shown in FIGS. 1-4, the filter 10 has several longitudinal ribs 12 supporting a first and second filter element or lattice 14 and 16. For the sake of drawing clarity, all of the ribs and the wires of filter elements have not been illustrated. Of course, there may be many filter elements or lattices, arranged in whatever preferred design is selected. In the arrangement shown in FIGS. 1-4, the filter elements 14 and 16 have a minimal number of converging wires.

One benefit of a design having more than one filter element coupled by longitudinal ribs is that the vascular filter 10 tends to deploy and align itself properly with the axis of the body passage or blood vessel.

In addition, the filter may be provided with a set of circumferential resilient supports, adapted to both hold the vascular filter in place, and also to ultimately hold open the body passage when the filter is converted into a stent.

As shown in FIG. 1, the filter elements 14 and 16 are held together by removable clamps 22. The clamps 22 are locked by pins 26, and both the pins 26 and clamps 22 have removal hooks 18 and 20 attached.

Before the filter is delivered and deployed in the patient's body, it is first loaded into a delivery catheter. In the distal tip of the catheter, at least one vascular fiter is initially arranged in a compressed state. As an alternative, it is also possible that the filter is pushed along the entire length of the catheter from its proximal end to its distal end, after the catheter distal end has been advanced to the desired position. Preferably the filter is packed, in a compressed state, in transport packaging forming a covering. The vascular filter may be ejected from the distal tip of the catheter by a pushing wire and introduced into a blood vessel. Due to the release from the radially compressive force imposed by the catheter lumen at the distal tip of the catheter, the vascular filter will tend to expand resiliently to obtain an expanded shape. Liquid inside the blood vessel can pass through in an unimpeded fashion, but thrombus will tend to be intercepted by one of the two filter lattices.

An advantage of this configuration is that it provides two filter elements for intercepting thrombus moving inside a blood vessel, which may be more effective than one. In addition, due to the configuration of the ribs which extend along the internal wall of the blood vessel, no free ends are presented which might damage the internal wall of the blood vessel. The configuration of the vascular filter according to the embodiment illustrated is consequently designed so as to minimize any distress or damage to the blood vessel inside of which it has been arranged. As filter elements have been arranged on either side of the ribs and consequently a symmetrical shape has been obtained, there is no difference in the performance of the filter regarding the direction from which this vascular filter 10 has been placed inside the blood vessel.

As has been illustrated, the grid shape of each of the filters is such that each of the ribs is connected with a number of the components of these filters. Furthermore, each of the ribs is connected with both filters on either side. Due to this configuration, an added safety feature is that the filter has a fail-safe design.

In addition, tipping over or misaligmnent of either filter is less likely due to the more or less tubular shape into which the ribs have been arranged so that positioning of the vascular filter 10 inside the blood vessel can take place with unprecedented stability and reliability.

The vascular filter 10 is preferably made of a very resilient material, like nitinol. Following the ejection from the distal tip of the catheter, filter 10 can expand and will be pressed against the internal wall of the blood vessel.

When the physician decides to transform the vascular filter into a stent, a catheter may be reinserted to a position near the filter. A guidewire with a hook can be used to pull the hook 20 attached to a locking pin 26. With the removal of the locking pin 26, the ends of the filter element collapse together, and the clamp 22 loses its purchase. The clamp 22 and locking pin 26 are then pulled by their attached hooks 18 and 20 out through the catheter, and the members forming filter elements 14 and 16 resiliently expand as in FIGS. 2-3. The resulting configuration is one of a resilient tubular stent 28 defining an open through lumen, as shown in FIGS. 4 and 4A.

The locking pin 26 and clamp22 at the other end of the filter may be accessed and removed by approaching the filter from the other vascular direction.

Another embodiment of the present invention is illustrated in FIGS. 5-10. The vascular filter 30 is shown having a “lobster pot” configuration including a number of longitudinal ribs 42, as well as transverse or circumferential support members.

A pair of hooks 38 and 40 are provided at the proximal and distal ends for the filter. The hooks 38 and 40 may of course be formed as a shaped extension of one of the filter wires or ribs 42. As shown in FIG. 5, both hooks 38 and 40 preferably extend from a center region of a filter element 44 in a proximal direction. This feature offers the advantage of releasing both filter elements 44 into the stent configuration with a catheter approaching the filter from only one direction.

The wires of each filter lattice 44 are held together by closing wires 52.

A catheter 32 and snare loop 34 may be used to convert the filter 30 into a stent configuration. After the snare 34 catches the proximal hook 38, it pulls the hook 38 and the closing wires 52 at the ends of the filter wires into the distal end of the catheter 32, as shown in FIG. 6. Inside the catheter distal end are a series of cutting members or knives 50, adapted to cut the closing wires 52 of the filter 30. When the closing wires 52 are severed, the filter wires resiliently expand to form the desired tubular stent configuration. Of course, the hooks 38 and 40 are specifically arranged to be flat against the body vessel wall in the stent configuration.

As shown in FIGS. 7-8, the distal end of the filter is released in a similar manner, and the resulting stent is shown in FIG. 9.

Yet another embodiment of the present invention is shown in FIGS. 11-12. The vascular filter is a hybrid combination of a central resilient “self-expanding” portion 54 flanked by two “balloon expandable” portions 62.

The self-expanding central portion 54 always tends to resiliently expand, being made for example of nitinol, while the balloon expandable portions 62 tend to remain compressed until forcibly expanded, being made for example of stainless steel.

The self-expanding filter portion 54 is permanently affixed to the balloon expandable stent portions 62, which may be affixed to a pair of hooks or loops 60 for maneuvering the device. The components may be affixed for example by welding.

When the physician decides to convert the filter into a stent, the balloon expandable stent or collar portions 62 are forcibly expanded such as by a balloon 66 of a balloon catheter 68, as shown in FIG. 12.

One advantage of the embodiment of a vascular filter according to the present invention is that the loop 60 may be used to later remove the vascular filter. Loops 60 can thus serve as a target for a hook-shaped extraction element, in order to remove the vascular filter. The hook-shaped extraction body (not shown) may engage the loop, and pull the entire vascular filter back into a catheter enveloping the extraction element.

After reading the above, many possible embodiments of a vascular filter that is convertible into a medical device forming an open lumen, other embodiments, and features will occur to one of ordinary skill in the field. All of these are to be considered as falling within the scope of the attached claims. It is for instance possible to use a vascular filter which has a different shape than the one described above. It is also possible to use a more conventional single vascular filter without the double filter feature. The vascular filter also does not need to comprise ribs extending in an axial direction in relation to the blood vessel.

It should be understood that an unlimited number of configurations for the present invention could be realized. The foregoing discussion describes merely exemplary embodiments illustrating the principles of the present invention, the scope of which is recited in the following claims. Those skilled in the art will readily recognize from the description, claims, and drawings that numerous changes and modifications can be made without departing from the spirit and scope of the invention 

What is claimed is:
 1. A vascular filter capable of converting into a tubular stent, comprising: a resilient lattice that tends to expand from a compressed shape to an expanded shape; a proximal and distal balloon-expandable stent affixed to proximal and distal ends of the resilient lattice, the balloon-expandable stents having an initial crimped diameter and tending to retain said crimped diameter; wherein the balloon-expandable stents to hold the proximal and distal ends of the resilient lattice closed to a relatively small profile, and being capable of being forcibly expanded to a larger diameter, such that the lattice and stents form a tubular composite stent defining an open lumen.
 2. A vascular filter capable of converting into a tubular stent comprising: a balloon-expandable stent portion having an initial crimped dimension and tending to retain said crimped dimension; the stent portion being capable of being forcibly expanded to a larger expanded dimension having a tubular shape, and tending thereafter to retain said expanded dimension; and a resilient portion affixed to the stent portion, tending to expand from a compressed shape to an expanded shape, such that the resilient portion has a shape when deployed that is generally tubular at one end and curves inward to the crimped dimension where the resilient portion is joined with the stent portion; and defining in the expanded shape a plurality of filter cells extending outward from the stent portion, tending to capture thrombus; wherein after the stent portion is forcibly expanded, the stent portion and resilient portion form a tubular composite stent defining an open lumen.
 3. A medical device for use in a body vessel of a patient, having a filter configuration and a stent configuration, comprising: a resilient portion affixed to an inelastic portion; the medical device extending between first and second ends and defining a length, and having an initial compressed state, a deployed filter state, and an expanded stent state; in the initial compressed state, the resilient portion and inelastic portion each having a major dimension at right angle to said length that is less than an initial compressed width; in the deployed filter state, the inelastic portion tends to retain its initial compressed width, and the resilient portion tends to expand at one end to an expanded deployed diameter, and the medical device defines a plurality of filter cells for capturing thrombus; in the expanded stent state, the inelastic portion has been forcibly expanded from its initial compressed diameter to an expanded deployed diameter, such that the resilient portion and inelastic portion form a tubular stent defining an open lumen extending between the first and second ends.
 4. The medical device of claim 3, wherein the resilient portion is made of nitinol.
 5. The medical device of claim 3, wherein the inelastic portion is made of stainless steel.
 6. The medical device of claim 3, further comprising a second inelastic stent portion affixed to an end of the resilient portion opposite from the first inelastic portion.
 7. The medical device of claim 3, further comprising at least one anchor affixed to the resilient portion, tending to inhibit motion of the medical device within a body vessel. 